Sensors such as load cell and pressure or torque sensors typically come in various forms that allow a physical condition such as force or pressure or torque to be measured. The influence of the condition is converted to an electrical signal that varies according to the magnitude of the sensed condition or quality.
Such types of sensor can use strain gages attached to an elastically deformable member. The strain gage is deformed with the deformable member and this deformation changes the resistance of the gage or gages. By connecting the gages into a Wheatstone bridge circuit, a change in resistance unbalances the bridge and produces an output representing applied load, torque or pressure when properly calibrated. Sensor elements other than variable resistance strain gages can be used.
Such sensors have been used in applications requiring the active elements to be hermetically sealed to protect them from potentially damaging environmental conditions such as the high temperatures associated with autoclaving or sterilization in a medical setting. A closed cell for the sensor components and associated electronics is typically created by two body elements, one of which includes a “header,” i.e., a group of pin-like insulated conductors passing through a wall of the body part and into the interior. This body part must be attached to a second, mating body part carrying the flexure element and the associated circuitry, mated and secured to each other such as by welding. This approach is only achievable on larger devices where overall size and shape allow for separate header and flexure components to be welded together.